Rotary blower



Oct. 23, 1962 G. P.v HANLEY E'I'AL ROTARY BLOWER 2 Sheets-Sheet 1 FiledJan. 12, 1960 INVENTORS @af Oct. 23, 1962 G. P. HANLEY ETAL 3,059,835

ROTARY BLOWER Filed Jan. 12, 1960 2 Sheets-Sheet 2 INVENTORS" ATTOE/V'yUnited States Patent O 3,059,335 RGTARY BLWER George P. Hanley,Northville, and Kenneth L. Huising,

Plymouth, Mich., assignors to General Motors Corporation, Detroit,lt/lich., a corporation of Delaware Filed lan. 12, 1960, @ein No. 2{92714 Claims. (Cl. 23u-itil) This invention relates to rotary blowers ofpumps of the positive displacement type, and more particularly to ablower of the type having two synchronously driven multi-lobed impellersor rotors, such blowers being particularly adapted among other uses forsupplying scavenging and charging air to a two-cycle internal combustionengine.

In such rotary blowers, the maintenance of minimum clearances betweenthe rotors and between the rotors and their housings is essential tomaximum volumetric efficiency. On the other hand, the providedclearances must normally be suliciently large to prevent actual contactbetween these parts. Otherwise, the high relative rubbing velocity ofthe metal-to-metal surfaces will develop high temperatures and excessivewear rapid-ly followed by seizure, welding or galling of the surfaces.Moreover, it is diiiicult to maintain such clearances at their desireddesign minimum in service. Operational deviations occur as a result ofdifferential thermal expansion of the various blower parts, elasticdeformations from various causes, wear of the driving gear and bearingsand cumulative tolerances resulting from manufacturing and assemblyerrors. To insure sutiicient clearances under all operating conditions,expensive machining operations have been required to obtain thenecessary accuracy of the various blower components. In the past, ratherexpensive close tolerance bearing arrangements have also been used inorder to maintain the necessary clearances between the rotors andbetween the rotors and their housings.

The invention contemplates an improved blower of the type describedhaving a lrotor configuration permitting wider latitude in manufacturingtolerances and variation in the displacement characteristic of theblower by simple changes in the addendum and dedendum dimensions of therotors with corresponding changes in the root contour of the impellerand in the mating surfaces of the rotor housing having a blower housingstructure permitting maximum mounting versatility and suiiicientrigidity to minimize elastic ldeformations due to assembly or operatingconditions; and having relatively simple, inexpensive bearing means forsupporting and maintaining the clearances of the lrotor assemblies withrespect to each other and to the blower housing members. These factorsall contribute to providing a blower which is Irelatively simple andinexpensive to manu-facture, and has a high volumetric efficiency.

The foregoing and other objects, advantages and features of theinvention will be more thoroughly understood and apparent vfrom thefollowing description of a preferred embodiment thereof, reference beingmade therein to the accompanying drawings, in which:

FIGURE 1 is a transverse sectional view showing the blower of theinvention mounted on a two-cycle internal combustion engine of theuniflow scavenged type;

FIGURE 2 is an elevational end view of the blower as viewed in FIGURE lwith portions thereof broken ICC away to show certain details of thebearing construction of the invention in elevation and in section; and

FIGURE 3 is an elevational side View of the blower taken in the plane ofthe line 3 3 of FIGURE l with portions thereof broken away and insection.

Referring more particularly to FIGURE 1 of the draw ings, an engineyframe or block member for a two-cycle internal combustion engine isindicated generally at lll. The block lll delines an air box 1l whichextends longitudinally of the engine between a lower crankcase definingportion 12 and an upper cylinder supporting portion i3. An engine drivenblower 30 is mounted on one side of the upper portion of the engineframe and is adapted to supply pressurizexi scavenging and charging air-to the block defined air box. The engine frame is preferablysymmetrical about its longitudinal vertical plane to provide alternative:blower mounting locations on either side of the engine in accordancewith the teaching of copending United States patent application SerialNo. 34,728, tiled, lune 8, 1960 in the names of George W. Conover,Kenneth L. Hulsing and Joseph Koehler and entitled Internal CombustionEngine.

rl`he air box li embraces several inline cylinder liners la which areslidably mounted and supported by the upper and lower block portions inaligned ports 15, l5 and lo. Each cylinder liner 14 has acircumferential belt of inlet ports 17 intermediate its ends. Theseports are connected directly to the air box proper. A cylinder head lillis secured to the upper face of the cylinder vblock and closes the upperend of the several cylinders. A piston 19 is reciprocahly mounted ineach of the cylinder liners and cooperates with the closed end thereofto deine `an expansible c-ombustion chamber 20. The lpiston is connectedin a conventional manner by a wrist pin 21 and a connecting rod 22 tothe engine crankshaft, not shown. Reciprocation of Jthe several pistons30 within their respective cylinders serves to control the admission ofscavenging and charging air through the inlet ports 17 into suchcylinders. This provides uniflow scavenging of the combustion gasesthrough exhaust valves, not show-n, which are reciprocably mounted inthe cylinder head and control the opening of ports leading to suitableexhaust passages and manifolds, also not shown. Such exhaust valves areoperated in a conventional manner by a camshaft 38 through conventionalvalve actuating mechanisms of the overhead .rocker type which are notshown except for one cam follower tappet 40.

Referring now to the several FIGURES 1-3, the blower Sil includes ahousing 31 comprising an intermediate liousing member 32 and twoidentical and interchangeable end plates 33 and 34. These end plates aresecured to opposite ends of the intermediate housing member 32 andcooperate `therewith to denne a pumping chamber 35. The side of theintermediate housing member 32 opposite the engine frame has inlet ports36 extending therethrough and supports an air in- .let housing member37. The air inlet housing 37 pivotally supports an engine shutdown valve38 which is biased by a spring 39 toward a closed shutdown position andis normally latched in its open position shown in broken line `fornormal engine operation. The engine adjacent side of the intermediatehousing member is provided with a mounting flange 40 which mates withthe blower mounting pads 41 of the engine frame and is supportedvertically by a laterally extending shoulder defining boss 42. Theengine mounting side of the intermediate housing member is provided witha pressurized air outlet at 43 which mates with and is connected to theengine air box through a port 44 defined by and extending through Itheside Wall of the engine block.

A pair of cooperating two-lobed impellers i5 are rotatably supportedwithin each lblower compartment $5 and are driven to provide pumpingdisplacement of air from the compressor inlet to its outlet d3. Theimpellers 45 have mating involute profiles which may be formed withconventional gear tooth cutting machinery. This in in contrast to thevery expensive and diflicu-lt machining operations which must be done inmanufacturing impellers having either straight or helical lobes ofconventional Roots type cross-section. To meet the scavenging airrequirements of the different engine applications, the displacementcharacteristics of the impellers may be changed as needed by varying themating addendum and dedendum diameters of the impellers, that is, byvarying the outer diameters of the rotors and making correspondingchanges in the mating surfaces i7 of the housing and makingcorresponding changes in root contour 1;8. This may be accomplishedwithout changing the precision mating involute profiles. Thus the sameelements may be machined by proper Setting to provide the differentscavenging and accessory air requirements for a wide range ofinstallations. This is in contrast to conventional Roots blowers whereindifferent drive gears are required to provide different pumping ratiosfor a given shaft spacing. To provide some latitude in machiningtolerances and to insure proper sealing with minimum running clearancesbetween the impellers and the mating housing surfaces under runningconditions, each peripheral portion of the impellers is provided withtwo longitudinally extending grooves it? which provide wearaccommodating ribs Sti and S'. During the initial breaking-in periods,these ribs rapidly wear in to provide the proper clearances if anymetalto-metal scung occurs between the several members. Proper sealingclearance ymay also be provided between the several impeller and housingsurfaces by coating these members with a `suitable high temperatureresistant grease in assembly.

The end plates and the intermediate housing member are preferably castof aluminum. With precision permanent type molds, such castings requirea minimum of dimensional iinishings. A plurality of reinforcingcompression heat-transferring ri-bs 32 extend between the inlet andoutlet sides of the intermediate housing member 3?. and preventexcessive elastic distortion of the member due to the generated airpressure on the discharge side of the housing. The identical end plates33 and 34 each comprise a web 69 defining the end wall of the blowerchamber 35 and a peripheral flange 70 extending therefrom opposite theadjacent end of the intermediate Ahousing member. These peripheralflanges of the end plates 33 and 34 are pilot dowelled at 5l and securedto the mating end faces of the intermediate housing member 32 by aplurality of bolts 52. Each end plate has two spaced parallel bores 53extending therethrough adjacent their upper and lower ends, as viewed inFIGURES l and 2. Bolts S4 inserted in these bores threadably engagetapped holes provided in the blower mounting pad of the cylinder block.iIn conjunction with the block-defined boss 42j, these bolts thus serveto support the assembled blower unit in its mounted position on the sideof the block.

Stub shafts 5'5 and 56 are rigidly secured to, carried by and projectfrom opposite ends of each impeller 45. These stub shafts are rotatablyjournaled in parallel aligned bores 58 which extend through journaldefining bosses or projections 71 and '72 upstanding from the webs ofeach end plate 33 and 34. The journal bores 58 of each end plate areintersected by and pressure lubricated through parallel passages 62j tomaintain the stud shafts and their respective impellers in properposition radially of the journals. These passages are interconnected bya third passage `63 which extends therebetween closely adjacent thejournals 58. The ends of the passages 62` opposite their respectivejournals open on the engine mounting faces 66 of the end plate. Thelower of these two passages in each end plate is connected to a drilledpassage 64 which extends transversely of and intersects the mainlongitudinally extending oil supply gallery 65 of the engine block.

Suitable face-type oil and compression seal rings 59 seal the shafts andend plate journals with respect to the blower chamber. These seal ringsembrace the shafts and are interposed between the shaft mounting hubs ofthe impellers and the adjacent end plates. These rings are biased intosealing engagement with the adjacent end plates by springs 6% which arehoused within counterbored recesses 61 formed in the impeller shaftmounting hub. Counterbores 67 formed in the end plates adjacent theseals 59 are drained through passages 68 extending radially therefromthrough the journal bosses. This draining of the counterbores 67prevents the seal 59 from being subjected to oil pressure and equalizesoil flow in both directions along the journals from the oil inletpassages 62.

A third projection 73 extends outwardly of each end plate web 69intermediate the journal bosses 7l and 72. These several projections arepreferably finished flush with the peripheral flanges 37 of theirrespective end plates. The third projection 73 is coextensive with areinforcing rib '74- which extends transversely of the end plate web inparallel relation to the bosses defining the passages 62 and thosedefining the holes 53 for the blower mounting bolts. The rib '74- alsointersects the boss defining the oil passage 63. It will be noted thatthe several projections, the mounting bolts, the hole dening bosses andthe rib '7d serve to reinforce the web of each end plate against elasticdistortion, and particularly on the discharge side of the blower due tothe location of the oil passage bosses.

ln accordance with certain aspects of the invention, a thrust washer issecured by a self-locking bolt '76 to the end of each stub shaft 55.These washers are preferably of ground and hardened steel. in assembly,the outer washer mounting end faces of the stub shafts S'S are precisionlocated with respect to the adjacent axial end faces of their respectiveimpellers to provide proper sealing clearance between the end platechamber wall 69 and the axial end faces of the impellers and to providenecessary bearing clearance for the thrust washers with respect to themating aluminum end faces of their adjacent journal bosses 7i and 72. Acast iron thrust plate 78 is spacedly bolted by self-locking bolts 79 tothe end plate projections 7l, 72, and 73 with spacer washers Si)interposed therebetween. The several bolts 79 are disposed in flankingrelation to the thrust washers. ln addition to the several holes fromthe bolts 79, the thrust plate '78 is perforated to spacedly embrace theheads of the washer securing bolts 76. The thickness of the spacerwashers il@ is selected to provide the necessary bearing clearancesbetween the shaft carried thrust washers, the thrust plate and the endfaces of the adjacent journal bosses. These thrust bearing surfaces arepressure lubricated by ports 8l in the journal boss end faces. The ports81 intersect the oil supply passages 62 and thus continuously supplylubrication to the mating steel-to-aluminum surfaces of the thrustwasher and journal boss end face. Direct lubrication of the matingsteel-to-cast-iron surfaces of the thrust washers and thrust plate isaccomplished through a plurality of ports 82 in the rotating washer, theports ft2 being intermittently aligned with the supply port S1.

With this thrust plate bearing construction, the axial position of theimpellers and the related impeller-housing clearances are relativelyeasy to maintain in assembly being dependent on a very limited number ofpieces. By

providing such thrust control at a single location, suchimpeller-housing clearances are also maintainable within a proper rangeunder operational conditions since the provided single location thrustcontrol is not as susceptible to differential expansions between therotors and the housing assemblies. The impellers 45 are synchronouslydriven 'with respect to each other by two timing gears 83 and S3'preferably having helical teeth. The gears 83 and `835 are suitablykeyed or splined on the ends of the stub shafts 56 and secured theretoby self-locking stud bolts 34 and 85 and washers 86 and 87. One of thegears S3 or 83 may be directly driven olf the main gear train. However,in the illustrative embodiment, a spring support member 88 of aresilient coupling 89 is secured to the timing gear 83 by a plurality ofbolts 9i). The member S8 supports two sets of leaf springs 9i inparallel spaced relation. These spring sets resiliently engage thenarrower surface dimensions of an elliptical drive cam 92. The cam 92 isdrivingly splined at 93 to one end of a quill shaft 94 and the oppositeend of the quill shaft is drivingly connectible to the accessory geardrive train of the engine. The several bolts 90' also secure a retainerring 95 to the spring support member S8, This ring retains both thespring packs 911 and the driving cam 92 in assembled driving positionswithin the coupling 39. This resilient coupling serves to isolate theblower unit from torque fluctuations in the accessory gear drive andengine output.

A cover member 96 is secured in sealing relation to the end plate 34 bythe bolts 52. This cover member embraces the blower driving elements andis perforated to provide a flanged opening 97. This ange is normallysealed with respect to the accessory and timing gear housing of theengine to define an oil receiving compartment 98. ln addition to the oilfrom the shaft journals S8, this compartment also collects the oilsupplied to the gears through the ports 81 in the end plate 34. Theupper port 8l also supplies oil to the spring packs 9d throughintermittently aligned ports 99 in the gear 8f3. A second cover memberlili? is also secured to the end plate 33 by the end plate securingbolts V5'2. This cover is imperforate and defines a second oil receivingcompartment 101. The oil receiving compartments 97 and lill are bothdrained and vented through ports lil-Z extending through theirrespective end plate iianges 70. The ports v102` are located to maintaina gear tooth immersing oil level and mate with crankcase connected ports103 in the side wall of the engine block.

From the foregoing description of a preferred embodiment of theinvention, it will be apparent to those skilled in the art that variouschanges might be made therein without departing from the scope andspirit thereof as dened in the following claims.

We claim:

1. A positive displacement rotary blower comprising a pair of lobedimpellers, a housing defining a pumping chamber and rotatably mountingsaid impellers, said housing including an intermediate housing memberhaving an inlet port and an outlet port therein opening on oppositesides of said chamber with respect to a plane passing through a rotativeaxes of said impellers and two end plates secured to opposite ends ofsaid intermediate housing member and dening the end walls of saidpumping chamber, said end plates each having two spaced parallel bearingdelining portions, said bearing portions having co-planar end facesopposite said chamber and bearing bores extending therethrough, shaftjournal portions extending from, rigidly secured to and rotatablyjournaling said impellers in said end plate bearing bores, said journalportions at one end of said impeller projecting slightly beyond theadjacent end plate, timing gears drivingly connected to said projectingjournal ends in spaced relation to the adjacent co-planar end faces andengaged to drive said lobed impellers in cooperatively phasedintermeshed pumping relation to each other, drive means associated withone of said gears for driving said impellers to effect pumpingdisplacement from said inlet port to said outlet port, the shaftjournals at the opposite end of said impellers each having a hardenedthrust washer secured thereto, said washers each being in bearingrelation with the adjacent co-planar end face of one of the journalbearing defining portions, and a stationary thrust member secured inspaced parallel relation to said journal end faces and in bearingrelation to said washers, whereby said thrust washers and membersrestrain axial thrust movement of said impellers thereby maintainingsaid impellers in proper rotative sealing clearance with said end walls.

2. A positive displacement rotary blower comprising a housing defining apumping chamber, said housing inciuding an intermediate housing memberhaving an inlet port and an outlet port therein opening on oppositesides of said chamber, and two end plates secured to opposite ends ofsaid intermediate housing member and defining the end walls of saidpumping chamber, said end plates each having two spaced parallel bearingdening portions, said bearing portions having co-planar end facesopposite said chamber end walls and bearing bores extendingtherethrough, a pair of lobed impellers including shaft journal portionsextending therefrom, rigidly secured to and rotatably journaling saidimpellers in said end plate bearing bores, drive means associated withone end of said impellers and operable to drive said lobed impellers incooperatively phased intermeshed pumping relation to each other toeffect pumping displacement from said inlet port to said outlet port,the shaft journals at the opposite end of said impellers each having ahardened thrust washer secured thereto in bearing relation with the endface of the journal bearing defining portions in the end plate, and astationary thrust member secured in spaced parallel relation to saidjournal end faces and in bearing relation to said washers, said thrustwashers and members thereby restraining axial thrust movement of saidimpellers and maintaining said impellers in proper rotative sealingclearance with said end walls.

3. In a rotary blower, a housing deiining a pumping chamber and havingan inlet port and an outlet port therein opening on said chamber, animpeller rotatably mounted in said pumping chamber, said housingdefining two spaced end walls of said pumping chamber having endwisesealing clearance with said impeller, said end walls having alignedbearing defining portions, said bearing portions having bearing boresextending therethrough and at least one of said portions having abearing end face opposite said chamber, shaft journal portions extendingfrom, rigidly secured to and rotatably journaling said impeller in saidbearing bores, drive means associated with said impeller and operable todrive said impeller to effect pumping displacement from said inlet portto said outlet port, one of said shaft journals having a hardened thrustwasher secured to the end thereof in bearing relation with the adjacentend face of said one bearing delining portion, and a stationary thrustmember secured in spaced parallel relation to said one journal end faceand in bearing relation to said washer whereby said thrust washer andmember restrain axial thrust movement of said impeller and maintain saidimpeller in proper endwise rotative sealing clearance with said endwalls.

4. In a rotary blower, an aluminum housing dening a pumping chamber andhaving an inlet port and an outlet port therein opening on said chamber,an impeller rotatably mounted in and having normal sealing clearancewith said pumping chamber, said housing defining two spaced end walls ofsaid pumping chamber, said end walls having aligned bearing definingportions and said bearing portions having bearing bores extendingtherethrough and at least one of said portions having a bearing end faceopposite said chamber, shaft journal portions extending from, rigidlysecured to and rotatably journaling said impeller in said bearing boresto maintain said impeller in proper radial sealing clearance with saidhousing chamber, drive means associated with said impeller and operableto drive said impeller to effect pumping displacement from said inletport to said outlet port, a hardened steel thrust washer secured to theend of one of said shaft journals in bearing relation with the adjacentend face of said one bearing defining portion, and a stationary castiron thrust member secured in spaced parallel relation to said onejournal end face and in bearing relation to said washer whereby saidthrust washer and member restrain axial thrust movement of said impellerand maintain said impeller in proper endwise rotative sealing clearancewith said chamber defining end walls.

5. ln a rotary blower as defined in claim 4, passage means in said endwalls for supplying lubricant to and intersecting said bearing bores.

6. ln a rotary blower as defined in claim 5, a lubricant supply portintersecting said passage means and opening on said one end face, saidport directing lubricant between said end face and said washer, and saidwasher having at least one port extending therethrough andintermittently connectable with said end face port to direct oil betweensaid Washer and stationary member.

7. A positive displacement rotary blower comprising a housing defining apumping chamber and including an intermediate housing member having aninlet port and an outlet port opening on opposite sides of said chamberand two end plates secured to opposite ends of said intermediate housingmember and defining the end walls of said pumping chamber, said endplates each having two spaced parallel bearing defining portions, saidbearing portions having bearing bores extending therethrough and thebearing portions of at least one of said end plates having finishedco-planar bearing end faces opposite said chamber, a pair of lobedimpellers cooperatively intermeshed 'to effect pumping displacementbetween the inlet and outlet ports, journal portions extending from,rigidly secured to and rotatably journaling said impellers in said endplate bearing bores to maintain said impellers in rotative sealingclearance with respect to each other and radially with. respect to saidintermediate housing member, means for driving said impellers in phasedrelation to each other to effect pumping displacement from said inletport to said outlet port, a hardened thrust washer secured to the end ofthe shaft journals mounted in said one end plate, said washer being inbearing relation with the bearing end faces of said one end plate, and astationary thrust member secured in spaced parallel relation to saidjournal end faces and in bearing relation to said washers, said thrustwashers and members restraining axial thrust movement of said impellersthereby maintaining said impellers in proper rotative sealing clearancewith said end walls.

8. A positive displacement rotary blower as set forth in claim 7 whereinsaid end plates are of aluminum, said thrust washers are of hardenedsteel, and said thrust member is of cast iron.

9. A positive displacement rotary blower as set forth in claim 7,passage means in said end plates for supplying lubricant to andintersecting said bearing bores.

10. A positive displacement rotary blower as set forth in claim 9, alubricant supply port intersecting said passage means and opening on theend faces of said one plate, said ports directing lubricant between saidend faces and said washers, and said washers each having at least oneport extending therethrough and intermittently connectable `with saidend face ports to direct oil between said washers and stationary member.

11. A positive displacement rotary blower comprising a housing defininga pumping chamber and having an inlet port and an outlet port openingthereon, said housing including an intermediate housing member and twointerchangeable end plates each having a peripheral flange secured toopposite ends of said intermediate housing member and a web portiondefining opposite end walls of said pumping chamber, said end plateseach having two spaced parallel bearing defining portions extendingoutwardly from its web portion, said bearing portions having bearing endfaces opposite said chamber co-planar with the end faces of the endplate flange and bearing bores extending therethrough, two impellersrotatably mounted in said chamber and having rotative sealing clearanceswith respect to each other and cooperating to effect pumpingdisplacement between said inlet and outlet ports, said impellers eachhaving a plurality of intermeshing lobes extending longitudinallythereof, said lobes having side faces of involute form interconnectedoutwardly by an outer peripheral portion of constant radius spacedradially from said chamber defining surfaces of said intermediatemember, said peripheral portion having a plurality of ribs extendinglongitudinally thereof, said ribs having rotative sealing clearance withthe chamber defining surfaces of said intermediate member, the involuteside faces of each impeller being interconnected inwardly by rootsurfaces of constant radius defining sealing clearances with theperipheral ribs of the other impelier, journal portions extending from,rigidly secured to and rotatably journaling said impellers in said endplate bearing bores to maintain proper sealing clearances between saidimpellers and said intermediate housing, said journal portions at oneend of said impeller projecting beyond the adjacent end plate, helicaltiming gears driviugly connected to said projecting journal ends inspaced relation to the adjacent bearing end faces and engaged to drivesaid impellers in phased relation to each other, the shaft journals atthe opposite end of said impellers each have a thrust washer securedthereto, said washer being in bearing relation with the bearing endfaces of the journal bearing defining portions of the adjacent endplate, a stationary thrust member secured in spaced parallel relation tosaid bearing end faces and in bearing relation to said washers, saidthrust washers and member restraining axial thrust movement of saidimpellers thereby maintaining said impellers in proper rotative sealingclearance with said end walls, and drive means associated with one ofsaid gears for driving said impellers to effect pumping displacementfrom said inlet port to said outlet port.

12. A positive displacement rotary blower as set forth in claim l1wherein said end plates are of aluminum, said thrust washers are ofhardened steel, and said thrust member is of cast iron.

13. A positive displacement rotary blower as set forth in claim 1l, saidend plates each having two parallel lubricant supply passages thereinintersecting said bearing bores and a third passage extending betweensaid two passages, the passage-defining portions of said end platesreinforcing the outlet sides thereof, and means for supplyingpressurized oil to one of said passages.

14. A positive displacement rotary blower as set forth in claim 13, alubricant supply port intersecting said passage means and opening on theend faces of said plates, said ports adjacent said gears directinglubricant thereon and said ports adjacent said washers directinglubricant between said end faces and said washers, and said washers eachhaving at least one port extending therethrough and intermittentlyconnectable with said end face ports to direct oil between said washersand stationary member.

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